Proximal ear hole injury heals by limited regeneration during the early postnatal phase in mice

• Published in: Journal of anatomy 2023-03, Vol.242 (3), p.402-416
• Main Authors: Abarca‐Buis, René Fernando, Krötzsch, Edgar
• Format: Article
• Language: English
• Subjects: Adipose tissue; Animals; Blood vessels; Cartilage; Ear; Ear Auricle; ear growth; ear hole injury; elastic cartilage; Female; limited regeneration; Male; mammalian regeneration; Mammals; Mice; Mice, Inbred BALB C; Mice, Inbred C57BL; Original; Regeneration - physiology; RRID:AB_10971844; RRID:AB_1658868; RRID:AB_2336413; RRID:AB_2536522; RRID:AB_262054; RRID:AB_2630356; RRID:AB_778028; RRID:MGI:2160915; Wounds
• ISSN: 0021-8782; 1469-7580; 1469-7580
• DOI: 10.1111/joa.13782

Ear pinna is a particular feature of mammals that shows several repair responses depending on age. Two millimeter hole made in the pinna of middle‐aged female mice heals due to partial reconstitution of new tissues (limited regeneration), whereas a hole punched in the ear of young mice forms a scar tissue. In these studies, the injury is made in the center of the ear pinna, but little is known about the type of reparative response along the proximodistal polarity of the ear. This study evaluated the effect of pinna polarity, age, and sex in the ear hole‐repairing response in Balb/c mice. Proximal injuries were repaired more efficiently by limited regeneration than wounds made in the middle region. Non‐injured ear histological analysis revealed a higher presence of muscle, adipose tissue, cartilage, and larger blood vessels in the proximal ear area, which could influence ear hole closure by limited regeneration. To evaluate the healing response during ear growth, we punched a standard hole in the proximal area of the ear on postnatal day 21 and 8‐month‐old mice (adults). Thirty‐five days after the wound, both groups reached the same wound closure, despite the greater proportional size of holes made in the younger mice. Ear growth also improved ear hole closure in male mice. These results suggest that ear growth accelerates hole closure, providing an example of enhanced regenerative abilities in growing structures. Finally, hole closure kinetics in the growing ear indicated an early re‐differentiation phase exhibited at 14 days post‐wound. In conclusion, ear topography and growth positively influenced the healing response to ear holes, making it a tractable model to study in mammals. The proximal region of mice pinnae exhibited more cartilage, muscle, and adipose tissue, as well as larger blood vessels compared to the middle region. Two millimeter ear hole punched in the proximal region ear closed more efficiently than holes made in middle, suggesting a differential healing response in these regions. Healing was also improved when a proximal hole was made in growing mice compared to adult mice. Thus, anatomic position and ear growth positively influenced ear healing.